Vibrator



C. F. COAKE VIBRATOR 2 SHEETS-SHEET 1 Filed April 18, 1946 R w W W. i E

w p J M a Q M 1 w! j 0 K 2 0 5 e o 6 7 a 4/ 5 5 M CHARLES F. COAKE ATTORNEY Dec. 11, 1951 F, COAKE 2,578,640

VIBRATOR Filed April 18, 1946 2 SHEETS-SHEET 2 5a INVENTOR.

CHARLES F. COAKE BY 1 7i ATTORNEY Patented Dec. 11, 1951 VIBRATOR Charles F. Coake, Indianapolis, Ind., assignor to Senn Corporation, New Augusta,

ration of Indiana Ind., a corpo- Application April 18, 1946, Serial No. 663,199

3 Claims.

This invention relates to electromagnetic vibrators and is a continuation-in-part of my application Serial No. 532,962 filed April 27, 1944, now Patent No. 2,483,085, September 27, 1949.

An object of the present invention is to simplify the construction and increase the operating efliciency of electromagnetic vibrators.

Another object of the invention is to maintain the maximum contact area between the contacts of an electromagnetic vibrator under all operating conditions.

Another object is to provide a vibrator having cooperating inner and outer contact arms in which the ratio of compliances of said arms is such as to maintain their contacting surfaces parallel to each other under all conditions of use.

Another object is to provide a novel construction and mounting of contact arms in a vibrator of the foregoing type, whereby the eifective length and tuning of said arms is maintained regardless of slight variations in the point of attachment of the arms in the vibrator assembly.

Still another object is to provide a novel type of electromagnetic vibrator which dispenses entirely with the conventional stack-type vibrator assembly and provides a basically novel structure in which the principal cooperating parts are fixed to a metallic frame by means of welding and similar operations.

A further object is to provide a vibrator structure which may be assembled in a manner comparable to the procedure followed in the manufacture of miniature vacuum tubes whereby an extremely strong structure may be combined with the desirable feature of very small dimensions.

Another object is to provide a vibrator in which a magnetic circuit of low reluctance is obtained by means of a novel frame member which also forms the principal structural member of the complete assembly supporting all of the other cooperating elements of the system.

A further object is to provide an electromagnetic vibrator of the foregoing type having novel and improved details of construction and features of operation.

Various other objects and advantages will be apparent as the nature of the invention is more fully disclosed.

Heretofore, electromagnetic vibrators have usually been built and assembled on the stack principle. That is, the principal operative elements including the vibratory reed, the various spring contact arms, portions of the frame, etc. have been provided with suitably aligned holes and were clamped together by means of stack screws with interposed spacer members providing the proper spacing between the several stacked elements. Such a vibrator possesses a number of disadvantages, including the following: The structure is relatively complex and its assembly requires a great deal of manual labor; the distance between the cooperating elements is determined by the spacer members which have to be of uniform thickness and this condition is difficult to fulfill in quantity production, particularly when the spacer members are made of synthetic resins which may change their thickness even after the assembly is completed; and this type of construction is relatively bulky and makes the manufacture of vibrators of small dimensions practically impossible.

The foregoing disadvantages of stack type vibrators have been accentuated by the recent trend in vibrator design directed to the construction of vibrators of very small dimensions. This trend developed when the essential components of radio receivers and transmitters, such as vacuum tubes, condensers, etc. became available and permitted the development of apparatus of great compactness as in the case of automobile and portable receivers of all types. Furthermore, in recent years extremely small portable radio receivers, the so-called personal radios and small vacuum-tube operated hearing aid devices have been placed on the market in large quantities and these devices have created a demand for vibrators of greatly reduced dimensions which so far the industry has been unable to satisfy. Although these problems were well known, and various suggestions and proposals were made to eliminate the difficulties and disadvantages inherent in conventional vibrator structures, none of these suggestions and proposals has been completely satisfactory and successful on a practical and commercial scale.

The present invention overcomes the abovementioned and other disadvantages of the prior art and provides a novel and improved electromagnetic vibrator which possesses all the advantages enumerated in the foregoing objects of the invention as well as numerous other advantages of simplicity of manufacture and assembly and increased operating efficiency, as will be hereinafter more fully described.

Although the novel features which are characteristic of this invention are set forth more in detail in the claims appended hereto, the nature and scope of the invention may be better understood by referring to the following description, taken in connection with the accompanying drawings forming a part thereof, in which certain specific embodiments have been set forth for purposes of illustration.

In the drawings:

Fig. 1 is a longitudinal sectional view of an electromagnetic vibrator embodying the present invention;

Fig. 2 is an exploded perspective View of the vibratory reed and contact assembly of the vibrator;

Fig. 3 is a perspective view of a modified form of reed-contact assembly;

Fig. 4 is a diagrammatic view of the cooperating inner and outer contact members of Fig. 3;

Fig. 5 is a perspective view showing another form of reed-contact assembly;

Fig. 6 is a diagrammatic view of the cooperating inner and outer contact members of Fig. 5;

and 7 Figs. 7 and 8 illustrate still another embodiment of the invention, the former being a perspective view of the modified reed-contact assembly and the latter being a diagrammatic view of the cooperating contact members thereof.

In the following description certain specific terms are used for convenience in referring to the various details of the invention. These terms, however, are to be interpreted as broadly as the state of the art will permit.

In the drawings, Figs. 1 and 2 show an elec tromagnetic vibrator comprising a pair of elongated magnetic frame members lii supporting a driver coil 12, a vibratory reed l3 secured to base plates M which are seated in an insulating disc I5, inner contact arms it which are secured to opposite sides of the reed I3, and outer contact arms I! which cooperate with the respective inner arms I6 as hereinafter more fully described.

The magnetic frame members It are preferably stamped out of sheet metal and are curved transversely throughout their length. Each frame member has a pair of outwardly extending arms 13 which overlap and are welded to the corresponding arms of the other frame member when the two members are brought together as shown in Fig. 1. The ends of the frame members adjacent the arms l8 comprise arcuate collars i9 which partly surround the driver coil 12 and are secured as by welding to a disc as of magnetic material which is attached to the core 2| on which the coil [2 is wound. The opposite end of each frame member H! has an arcuate surface 22 which is adapted to be welded to the base plates M as hereinafter described.

The vibratory reed I3 is formed with an upwardly tapering width and has an armature Il a. of magnetic material secured to its upper or free end as by welding. When the vibrator is assembled, as shown in Fig. 1, the armature 43a is encompassed by the arms !8 of the magnetic frame members IQ and its ends are spaced only slightly from said arms, thus forming a magnetic flux path of low reluctance which increases the sensitivity of the instrument. The lower extremity of the reed ends in two extensions or cars 23 connected with the body of the reed by means of weakened portions it constituting hinges which facilitate setting the reed in vibration upon energization of the driver coil [2. The ears 23 of the reed are seated between ears 2?; depending from the base plates l4 and secured in place as by welding. The depending ears 2% seat in radial slots 21 in the insulating disc l5.

The plates :4 contain holes 28 which fit around diametrically opposed bosses 29 in the disc 15.

The two inner contact arms it, which are secured to opposite sides of the vibratory reed 13, are preferably stamped out of flexible sheet metal and each comprises a pair of spaced parallel side arms 3| having their ends connected by top and bottom yokes or cross arms 32 and 33, respectively, and an inner arm or tongue 34 projecting from the center of the top yoke 32 into the space between side arms 3! and carrying a contact 35 having a flat contact surface. The bottom yokes 33 are bent transversely along a line '38 and the portions of said yokes below the bend 3e are secured to the reed [3 by riveting or welding, so that the entire contact arm 15 above the bend 35 stands out from the reed It and the two contact arms it together form a V- shape as shown in Fig. l. A feature of this construction is that the bend line 35 in the contact arm 16 is in the comparatively rigid part of the arm, namely in the bottom yoke 33, below the lower ends of the flexible side arms 3|. Hence the predetermined efiective length and tunin of the side arms 3! remains unchanged even though the precise location of the bend 36 may vary slightly in different stamping operations and regardless of any variations in the effective width of the flat portion of the yoke 33 below the bend line 36 due to variations in welding or riveting pressure.

The two outer contact arms ll each comprise a pair of spaced pins or side arms 38 having their outer or free ends connected as by welding to a bar 39 carrying a contact 46- having a flat contact surface which is adapted to co operate with the contact 35 of the adjacent inner contact arm 16. The lower ends of the pins 3's extend downwardly through spaced bosses at in the insulating disc 15 and are attached to small M-shaped plates 43 below the disc it. The pins 38 contain small flanges 45 which seat against the bosses 44 and thus determine the proper height of the contacts 48. The lower sur faces 22 of the frame members it are welded to the plates 14, as shown in Fig. 1. The electricai leads to the outer contact arms ll may be soldered to the M-shaped plates 43; while the electrical leads to the inner contact arms it may extend upwardly through bosses 29 in insulating disc 45 and be soldered to the base plates it. The pins or side arms 38 of the outer contact arms 4'. are bent transversely just above the flanges 45 to enable the contacts 40 to mate in flat faceto-face engagement with the contacts 35 of the respective inner contact arms I5, as shown in Figs. 1 and 2.

In accordance with a feature of the invention, the compliances (i. e., the reciprocal of stiffness) of the inner and outer contact arms l6 and I! of the vibrator are selected to maintain the contacts 35 and 4B of said arms parallel to each other throughout the working range, and thus prevent one contact from rocking on the other as the arms flex. Maximum contact area is thus maintained under all operating conditions and the contact eiiiciency and life is improved. The construction of the contact arms to achieve this result will be illustrated with reference to the cooperating inner and outer contact arms It and ii adjacent the right-hand side of Fig. 2, to the salient parts of which the reference letters caband c are applied in order to facilitate the description.

With referenc to Fig. 2 the compliance of the contact arm It is the sum of the compliances of the component parts of said arm. One of such component parts of the inner contact arm I6 is the portion of the side arms 3| from the base of the free side arms 3! to the line of the contact 35, which is designated a in Fig. 2. The other component part of said arm [6 is the U-shaped distance I) from the aforesaid line of the contact 35 around the yoke 32 and the tongue 34 to the contact 35 itself. The compliance of the outer contact arm ll is simply the straight compliance from the support of the arm to the contact Ml. In such case, when only one of the two cooperating contact arms contains a reverse bend, the ratio of compliances of the various parts of the arms in order to maintain parallel contacts through the working range is:

For example, if c is rigid (compliance zero) then b equals a. Hence the contact 35 would remain parallel to the rigid contact 40 if the compliances a and b are made equal. The formula may also be expressed thus: When only one of the coopcrating contact arms contains a reverse bend the compliance of the bent arm above the contact line is equal to the sum of the compliance of the remainder of that arm plus the compliance of the other arm. When the compliance ratio has the above characteristic the contact faces will remain parallel throughout the working range as the arms are flexed and their entire areas are available for carrying the current.

Figs. 3 and 4 illustrate a modified construction of the cooperating contact arms in which, however, the formula for determining the ratio of compliances is the same as above stated. In this embodiment of the invention the side arms 3| of the inner contact arms I6 do not have a top yoke (32 in Figs. 1 and 2) but have their outer free ends doubled over in the form of a reverse bend at and have contacts 35 secured to the extremities of both bent portions 50. Likewise the side arms 38 of outer contact arms I! do not have a connecting bar (39 in Figs. 1 and 2) but have contacts 4!! secured directly to each of the side arms 38 for cooperation with the contacts 35 of the respective inner contact arms I6. This construction is similar to that shown in Figs. 1 and 2, and the applicable formula is also:

where 12 represents the compliance of the bent arm 3! from the line of contact 35 around the bend to said contact 35; a represents the compliance of the remainder of arm 3!, and c represents the compliance of the cooperating arm 38, as illustrated diagrammatically in Fig. 4.

The construction illustrated in Figs. 5 and 6 differs from that of Figs. 3 and 4 only in that the side arms 38 of outer contact arms I! of Figs. 5 and 6 contain a reverse bend 5| and the contacts 38 are carried by the ends of the bent portlons 5!. In this case the formula for determining the ratio of compliances is:

where a and 17 represent the compliances of one contact arm below and above the contact line as in Fig. 4 and c and d represent the compliances of the cooperating contact arm below and above the contact line respectively, as illustrated diagrammatically in Fig. 6.

Figs. "1 and 8 illustrate a modification of the invention in which the side arms 38 of the outer contact arms contain a reverse bend 5| as in Figs.

6 4 and 5, but in which the side arms 3| of the inner contact arms are straight. This construction is thus reverse of that shown in Figs. 3 and 4 where it is the inner contact arms which are bent and the outer contact arms which are straight. In this case the formula also applies for determining the ratio of compliances, as illustrated diagrammatically in Fig. 8 where a and I) represent the compliances of the parts of the arm 38 below and above the contact line and 0 represents the compliance of the straight arm 31.

In all of the above examples the contact sur faces remain parallel to each other when the compliances cf the arms have the ratios specified. The contact pressure varies with the flexing of the arms, but the area of contact does not change. Contact wear is greatly reduced and the life of the contacts correspondingly increased.

Although certain specific embodiments have been shown and described herein for purposes of illustration, it will be evident to those skilled in the art that the invention is capable of various modifications and adaptations within the scope of the appended claims.

What is claimed is:

1. An electromagnetic vibrator comprising a vibratory reed, a pair of inner contact arms carrying contacts mounted on opposite sides of one end of said reed, and a pair of outer contact arms carrying contacts for engagement with the contacts of the respective inner contact arms mounted independently of and extending generally parallel to and in the same direction as said inner contact arms, all of said contact arms having reversely extending portions carrying their contacts and having compliances selected according to the formula a+d=b+c where a and. 0 represent the compliances of the respective cooperating contact arms from their support to their contact lines, and b and d represent the compliances of said contact arms from said contact lines around the reverse portions to said contacts.

2. An electromagnetic vibrator comprising a vibratory reed mounted to vibrate in a fixed path, an armature on the free end of said reed, and extending transverse to said path, a pair of inner contact arms carried on opposite sides of said reed standing out from said reed at an angle and containing fiat contacts, a pair of outer contact arms each supporting a fiat contact for engagement with the contacts of the respective inner contact arms, a magnetic frame having arms extending parallel to said reed on each side thereof and lying beyond and normal to its path of vibration, a driver coil mounted in said frame above said armature, and magnetic arms extending between said first arms on opposite sides of said armature and parallel to said path of vibration to form with said first arms a closed magnetic loop within which said armature vibrates, said last arms being closely spaced from the two ends of the armature along said path of vibration to form therewith a magnetic path of low reluctance.

3. An electromagnetic vibrator comprising a metal base plate, a vibratory reed secured to said plate and extending upwardly therefrom, an armature on the free end of said reed extending transverse to its path of vibration, a pair of inner contact arms mounted on opposite sides of said reed and supporting flat contacts, a pair of outer contact arms insulated from said base plate and supporting flat contacts for engagement with the contacts of the respective inner contact arms, a pair of elongated transversely curved magnetic frame members extending parallel to said reed on opposite sides thereof, lying beyond and normal to the path of vibration thereof and having their lower ends secured to said base plate, arouate collars on the other ends of said frame members above said armature forming a supporting ring parallel to said plate, a magnetic-disc carrying a driver coil secured between said arouate collars with the axis of said coil normal to the plane of said plate, and arms extending between said frame members closely spaced from the two ends of said armature along its path of vibration to form with said armature a magnetic path of low reluctance.

CHARLES F. COAKE.

REFERENCES CITED ihe following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 815,822 Herman Mar. 20, 1906 2,036,295 Pifiath Apr. 7, 1936 2,068,093 Terjesen Jan. 19, 1937 2,072,578 Barrett et al. Mar. 2, 1937 2,096,962 Dressel Oct. 26, 1937 2,197,607 Brown Apr. 16, 1940 2,200,064 James May 7, 1940 2,213,854 Wood Sept. 3, 1940 2,243,920 Philips June 3, 1941 2,297,403 Glassing et al. Sept. 29, 1942 2,334,769 Huetten Nov. 23, 1943 2,475,320 Coake Apr. 18, 1946 

